The present invention relates to a conductive material suitable as a gasket material for shielding the electromagnetic wave leaking mainly from electric devices and equipment and a method of manufacture thereof.
In recent years, electronics equipment including personal computers, television games, portable telephone, and the like have come to be widely used and the ownership thereof has extended into home applications. With the expansion of the use of these equipment from industrial fields to home applications, the problem that the electromagnetic wave leaking from these equipment may cause an operation error of other electronics equipment and radio wave interference for communication equipment has become an increasingly serious subject of discussion in mass media.
Under these circumstances, a demand is high in the electronics and related industries for an electromagnetic wave shielding material which exhibits an excellent masking effect for preventing various interferences of the electromagnetic waves leaking from such devices and equipment.
Generally, an especially serious problem of the electromagnetic wave generated from electronics devices and equipment derives from the electromagnetic wave leaking from the joints of the parts constituting a housing of the equipment and from the gaps between the doors mounted on the housing. Various forms of gaskets have so far been proposed for shielding the electromagnetic wave leaking therefrom.
A practical effect has been achieved to some degree by a gasket product having a compression resistance and a metal-like conductivity as a shielding material exhibiting a sufficient shielding capacity. Such a product, as shown in FIG. 1, is made of a foamed polyurethane material making up a rectangular parallelopipedal porous synthetic resin sheet 1 not plated with metal but adhesively wound with a metal-plated fiber cloth 2, and an adhesive layer 3 is formed on the whole or part surface of the fiber cloth, after which the releasing paper 4 is laid thereon. The foamed urethane material actually used, however, because of its high flexibility and cushion property, is materially so weak that the work of cutting the material into a thin strip with a specified width in a predetermined direction is considerably difficult from the technical standpoint. Such being the situation, a compression-molded foamed material is actually used which is permanently deformed by being thermally compressed to the desired thickness in order to attach a compression resistance.
Such a gasket material is manufatured by a method in which a parallelopipedal foamed polyurethane material mechanically slited in advance is wound with a metal plated fiber cloth having an adhesive. This manufacturing process requires considerable labor, resulting in an increased production cost.
The present invention has been developed in view of this present situation, and the object of the invention is to provide a conductive material and a method of fabrication thereof, which eliminates complicated steps required for fabricating conventional electromagnetic shield gasket materials and which can mass-produce a gasket material low in cost, uniform in quality and high in reliability.
The present inventors have developed this invention as a result of an intensive study to achieve the above-mentioned objects.
According to one aspect of the invention, there is provided a conductive material suitable as an electromagnetic shield gasket material in which an organic fiber-structured sheet and a porous synthetic resin sheet are integrally laid one on the other into a composite sheet and metallized.
According to a second aspect of the invention, there is provided a method of fabricating a conductive material suitable as an electromagnetic shield gasket, in which an organic fiber-structured sheet and a porous synthetic resin sheet are bonded one on the other, and the resulting composite sheet is plated with a metal.